This study will investigate the role of vitamin A in reproductive function. In male and female rats, the dietary content of the alcohol (retinol) and acid (retinoic acid) forms of the vitamin will be raised or lowered, and the consequences of such alterations on the onset of puberty, reproductive cycles, secretion of sex steroids, secretion of LH and reproductive organ morphology will be examined. In addition, plasma and liver vitamin A levels will be measured throughout the pubertal period, during the estrous cycle, during pregnancy, after gonadectomy and after treatment with sex steroids. The response of the secondary sex organs and the pituitary gland to sex hormones will be examined following manipulation of the dietary intake of both forms of vitamin A. By establising the role of vitamin A in reproductive function, it may be possible to use vitamin A levels as a diagnostic aid, or to regulate the dietary intake of vitamin A during menstrual dysfunction or during an abnormal pregnancy.